Pebble testing method and apparatus



y 7, 195.3 s. P. ROBINSON ETAL 2,544,328

PEBBLE TESTING METHOD AND APPARATUS I Filed Dec. 13. 1948 2 Sheets-Sheet l ELEVATOR 40 4| m 2 s 45 E m 1 i 5 LL] V111,, 34

52 I 54 1 INVENTORS \J s;P. ROBINSON -7 1 2 BY R. R. cows 7 ATTORNEYS July 7, 1953 S. P. ROBINSON EI'AL PEBBLE TESTING METHOD AND APPARATUS Filed Dec. 13. 1948 ELEVATOR 2 Sheets-Sheet 2 INVENTORS s. P, ROBINSON BY R. R. GOINS A TTORNEYS Patented July 7, 1953 UNITED TENT OFFICE PEBBLE TESTING METHOD AND APPARATUS Application December 13, 1948, Serial No. 64,936

11 Claims.

This invention relates to a pebble tester. In

.one of its more specific'aspects it relates to a method and apparatus for testing the physical strength of heat transfer pebbles.

One of the problems involved in the successful operation of heat exchangers utilizing solid the best heat exchange. It is highly desirable that the pebbles developed for pebble heat exchangers be as resistant to thermal and mechanioal shock as possible. development of suchpebbles, it is necessary to place sample pebbles under certain thermal and mechanical stresses as rapidly as possible during the testing period. Testing of pebbles in fixed bed operation has proved to be neither suitable nor practical.

An object of this invention is to provide a means for determining the strength of heat transfer pebbles; Another object of this invention is to provide a, means for subjecting heat transfer pebbles to thermal shock. Another object of this invention is to provide an improved method for subjecting heat transfer pebbles to thermal shock. Another object of this invention is to provide means for subjecting heat transfer pebbles to mechanical shock. Another object of this invention is to provide an improved method for subjecting heat transfer pebbles to mechanical shock.= Another object of this invention is to provide a means and method for testing the strength of pebbles for pebble heating systems. Another object of the invention is to provide a means and method for testing the strength of pebbles. for pebblecooling systems. Other and further objects and advantages will be apparent upon study of the accompanying disclosure.

We have inventeda device by which pebbles which are to be tested may be subjected to very great'ther'mal and mechanical shock at a very rapid rate. By the utilization of thisdevice we are able to rapidly determine the relative ability of any given pebbles-to withstand severe thermal and mehcanical shock.

More complete understanding of our invention will be obtained upon study of the accompanying diagrammatic drawings. Figure 1 of the drawing is a. vertical elevation, partially in section, of the preferred form of our device. Figure 2 is'an elevation, partially in section, of a modified form of the invention. Figure 3 is an elevation,- partially in section, of a second modification of our invention.

In the device schematically shown as Figure 1 of the drawing, heater It comprises a heat resistant conduit tube l2 which is encased'within an. electrical resistance element 13 which is in turn encased by insulation material It and heater chamber H5. The ends of resistance element I3 are connected with electrical transformer it by electrical lead lines I! and i8. Heater H is inclined from the horizontal by such an angle as will cause pebbles 19 to flow freely through con- For themost economic duit 52. An inclination of approximately 10 fromthe horizontal has proved to give the best flow of pebbles through the heater, although greater or lesser degrees of inclination will provide fairly good pebble flow. A-first conveyor means connects the lower end of heater II with the upper end of pebble compression applicator 21. The, first conveyor means comprises a conduit 22, extending from the lower end of heater i l to the lower portion of elevator 23, elevator 23, and conduit it which extends from the upper portion of elevator 23 to the upper portion of pebble compression applicator 2|. Cooling gas inlet conduits 25 communicate between a cooling fluid supply source (not shown) and the first conveyor means, preferably pebble conduit 22. Any

number of cooling conduits which is necessary to provide the amount of cooling fluid necessary for sudden cooling may be utilized. Efiluent outlet conduits 28 are provided in the first conveyor means, preferably downstream of the cooling conduits 25 in pebble conduit 22. A pebble feeder 2'? may be provided in conduit 22 so as to control the rate offiow of pebbles through heater I I and conduit 22. Pebble compression applicator 2i comprises a pebble feeder 28 in its upper end and a hard-surfaced pebble receiver member 29 disposed at least three and one-half feet vertical- 1y below feeder member 28. Receiver member 29 is preferably spaced from feeder member 28 by a vertical distance of at least six feet. Receiver member 29 is preferably inclined from the horizontal so as to allow gravity to substantially clear the surface of receiver member 29 and to move pebbles and fragments thereof to the lower end of member 29. A chamber 3| preferably eX- tends between pebble feeder 28 and receiver member 23. Pebble outlet opening 32 is provided in the lower end of receiver member 29. Pebble sorting means 33 comprises plate 34 which is disposed vertically below pebble outlet opening 32 of pebble compression applicator 2|. The surface of plate 33 is inclined toward outlet opening 35 therein. Extractor member 36 also forms a part of sorting means 33 and is disposed intermediate plate 34 and the upper end of heating chamber Extractor 35 is preferably a chamber disposed below a second conveyor means comprising pebble conduit 3'! extending between opening 35 and the upper end of heater ii C o-nduit 37 is provided with a false bottom 33 within extractor 36 so as to allow broken particles to fall tlierethrough.

In the operation of the device shown as Figure 1 of the drawings, pebbles I9 are passed into the upper end of heater H, which is inclined a few degrees from the horizontal, and are raised to a relatively high temperature therein ranging between about 1600 F. and about 3500 F. at a rate of between about 1000 F. and 1800 F. per minute. The heated pebbles fiow through heater .H and into pebble conduit 22 in which they are subjected to the cooling action of an inert fluid, preferably a gas, so as to cool the pebbles at a rate of between about 2000 F. and 3500 F. per minute. Use of air jets for cooling obtains a much more rapid rate of cooling of the pebbles than is obtained by dropping the pebbles into water or other liquid. When water is used, steam 1:.

effectively insulates the surface of the pebble and prevents emcient cooling. Effluent outlet conduits 26 are sufilciently large to provide the path of least resistance for the cooling gases out of conduit 22. The cooled pebbles are fed to elevator 23 by pebble feeder 2'! and are carried to the upperportionof elevator 23 and are there passed into the upper portion of conduit 24. Conduit 24 is inclined so as to allow the pebbles to flow downwardly therethrough by gravity. The lower "end portion of conduit 24 may act as a pebble collector from which the pebbles are fed by pebble feeder 28, positioned in a constricted portion thereof, and are passed into pebble compression applicator 2| wherein they are dropped a predetermined vertical distance onto the hard surfaced receiver member 29, the weight of the pebble furnishing the compression for the pebble. Unfractured pebbles flow downwardly over the surface of member 29 through outlet opening 32 and onto the surface of plate 34 of pebble sorting means33. Fractured particles of pebbles may roll off of the surface of member 29 or be removed from within chamber 3| by applying a jet of air or some similar flushing gas to the surface of plate 29 throughconduit so as to sweep the fractured particles downwardly over member 23 and through outlet opening 32. Fractured particles may be removed from the system at the surface of plate 34 or passed with the pebbles downwardly through opening 35 in plate 34 into conduit 31. The pebbles flow through conduit 31 intothe upper end of heater I to repeat the test cycle. Fractured particles of pebbles fall through the false bottom of conduit 31 into extractor 35 from which they are removed. The electrical current which is'passed through electrical resistance element l3 may be varied at transformer 5 so astoprovide thedesired temperature within heater ll. One modification which may be ap- 4 plied to the device of Figure l is that a false bottom may be provided in sorting plate 34, as shown in Figure 3, so as to allow broken particles to fall directly from outlet opening 32 into an extractor while conveying the unbroken pebbles into the upper portion of heater II. In the inclined arrangement of heater and conduits, the relation between pebble size and conduit size is critical only in that the conduit must be of such diameter as to allow the pebbles to flow therethrough. The conduits are preferably sized so as to be but slightly larger than the largest pebble in the system, Jamming of pebbles is thus substantially eliminated.

The device shown as Figure 2 of the drawings comprises a substantially vertically disposed heater 43 having a closed shell 4| and being provided in its upper end with pebble inlet conduit :32 and eifluent outlet conduit 43. Pebble outlet conduit 44 which is slightly larger than the diameter of the pebbl s is provided in the lower portion of heater '46) and heating fluid conduits '45 are also provided in thelower'portion of heater 43. Heater 43 may be provided with a separate combustion chamber'within the lower portion of chamber 43 or adjacent the periphery of heater is in its lower end portion. It is believed, however, that the most efficient heating is obtained by the injection of fuel directly into heater 4|] and by burning such fuel on the surface of pebbles passing downwardly through heater '40. Pebble feeder 4B is provided below the outlet end of pebble outlet conduit 44. Feeder. 46 is in the form of a flat plate 4? having'an outlet opening 48 in its side diametrically spaced from pebble outlet conduit 44. Rotation member 49 is provided with openings 5| which are slightly larger than the diameter of the pebblesand are disposed on a circle directly below pebble outlet conduit 44. Rotationmember 49 is mounted on a hollow shaft 52 through which cooling fluid, preferably a gas, is passed. Outlets 53 communicate between hollow shaft 52 and openings'fil-of rotation'member 63. A cooling fluid conduit-may also be directed against the lower surface of plate 4Tto lower its temperature and reduce erosion thereof. A first conveyor means comprises conduit 54 which communicates between opening 48 in plate 37 and the lower portion of elevator 55, also a part of the first conveyor means. Conduit 56, also a part of the first conveyor means, communicates between the upper portion .of elevator 55 and the top of pebble compression applicator 2|. Pebble feeder 28 is provided in the upper end of compression applicator 2| at the lower end of conduit 56. Compression applicator -2| is provided in its lower endwith a hard surfaced receiver member 29 which is disposed at an angle with the horizontal as discussed above in :connection with the device of Figure l. Outletopening 32 is provided at the lower .end'of receiver member 29. Sorting .means :33 is disposed vertically below'opening 32 and i providedwith a grill or false bottom 15'! .directly below opening 32. Extractor. :36 is provided below .false bottom 51. Plate 34 is .cli-sposed at an angle'ifrom the horizontal and is provided in its. lower end :with pebble outlet opening '35. Alsecond communication means communicates between pebble'sorting means 33 and the upper portion of heater 4|]:and comprises conduit .53 whichcommunicates between opening 35 of plate v34 and the lower portion-of elevator 59. Conduit 6|, also-a portion 101 the second conveyor means communicates beupper'portion of heater 40.

The device shown in Figure 2 of the drawings operates very similarly to that shown in Figure 1 of the drawings. Pebbles are injected into the upper portion of heater 40 and pass downwardly therethrough countercurrent the flow of hot combustion gas therethrough. A ortion of the heating is preferably obtained'by burning the fuel on the surface of the pebbles. Heated pebbles pass downwardlythrough pebble outlet conduit 44 and are received by openings 5| as rotation means 49 causes openings 5! to enter the same vertical plane as that in which pebble outlet conduit 44 i maintained. Cooling gas is directed through hollow shaft 52 and outlets 53 against pebbles in openings 5|, thus cooling the pebbles during their through opening 35, and are transported to the upper portion of heater 45 by means of conduit 58, elevator 59 and conduit 6|. Broken particles may be removed from compression applicator 2| by gravity which causes them to roll off the surface vof member 29 or by injecting a flushing gas along the surface of member 29 so as to blow the particles through outlet opening 32, thus allowing the particles to fall through the false bottom of plate 34 into extractor 36.

The modifications of our invention which have been described heretofore have been devoted-to apparatus used in testing pebbles for pebble heating apparatus. We areaware of the fact that heat exchange pebbles are also used in pebble cooler systems and the modification shown in Figure 3' of the drawing is used for the testing of the pebbles to be used in such cooling systems.

Cooler 6! comprisesa conduit member 62 extending centrally through cooler 5!. Conduit member 52 is surrounded by a cooling coil 63 having an inlet 64, preferably at the downstream end of coolerfi I, and an outlet 55 at the upstream end of cooler '6 I. Cooling coil 53 is enclosed within insulation 66 and chamber 61. A pebble feeder 58 is provided in pebble conduit 69 which communicates between the lower end of cooler 6| which is disposed at an angle from the horizontal and compression applicator l I. Heating fluid inlet conduits l2 communicate between a heating fluid supply source (not shown) and pebble conduit 69 at a point downstream of pebble feeder 58. Efiluent outlet conduits 13 are also provided in'pebble conduit 69. Pebble compression applicator H comprises a hard surfaced receiver member 29 which is disposed at an angle from the horizontal, preferably tilted away from the outletv end of conduit 69. Outlet opening 32 is provided in the lower end of member 29. Compresat one end by hinge l5. Compressor 14 is supported at its other end by spring member 16. A photoelectric cell ll, positioned in thebeam of a light source 80, is provided in the lower end of conduit 89 and communicates by electrical leads '18 with amplifier l9. Amplifier l9 communicates openi1ig32so as to allow particles to fall therethrough into extractor member 36. Pebble sorting means 33 is disposed at an angle from the horizontal and outlet opening 35 is provided in its lower end portion. The second conveyor means communicates between opening 35 and the upper end of cooler 6 l. The second conveyor means comprises conduit 84 which communicates between opening 35 and the lower portion of elevator 85 Conduit 86, also a part of the second conveyor 'meana'communicates between the upper portion of elevator 85 and the upper end of cooler 82. Pebble feeder 81 may be provided in conduit 8t intermediate its ends.

In the operation of the device shown in Figure 3 of the drawing, pebbles are inserted into theupper'endof cooler'ii'l and flow downwardly therethrough. Cooling fluid is, inserted into cooler ti through inlet 54 at any desirable'teinperature. In order to obtain best results, a cooling iiuid at a temperature ranging between about jl50 F. and -SOO F. is preferred. The cooled Si by feeder t8 and are brought in direct heat exchange with hot heating fluid from conduit 72. Pebble eeder t8 maybe provided in the lower portion of conduit 8G so as to control the velocity of pebble flow therethrou'gh. The pebbles are raised to a temperature between about 500 F. andQGO" F. by the heating'fiuid. The heating fluid is removed through heating effluent outlets l3 and the pebbles pass downwardly through conduit 59 and break the lightbeam directed onto photoelectric cell ll from light supply source 80 in the lower end portion of conduit 69. Amplifier i9 is energized by the break in the light beam and passes a current through time delay circuit 83 to solenoid 8| which forces compressor 14 V are removed through outlet opening 35.

pebbles are transported by means of conduit 84,

' .501 14 is disposed above member 29 and is hinged downwardly in time to contact the pebble on the surface of receiver member 29 and compress the pebble therebetween. The pebbles and broken particles'are removed from member 29 through outlet opening 32 and pass onto plate 34. Broken particles fall through false bottom 51 in plate 34 into extractor 36. Unbroken pebbles pass downwardly over the surface of plate 34 and The elevator 85, and conduit 86, to the upper end of cooler M where they are once again subjected to the test cycle; a

The pebble compressor applicator which is shown in Figure 3 of the drawings may be substituted for that shown inv the devices set forth in Figures 1 and 2 of the drawings. The method disclosedfor actuating compressor 14 is merely exemplary. Other means and methods maybe utilized for compressing pebbles without departing from the scope of the disclosure.

The heaters of Figure 1 and Figure 2 may be interchangeable. The outlet of the vertical heater should, however, be but slightly larger in diameter than the diameter of the pebbles tested.

That limitation is not placed on the inclined The gas which is injected into assua e wall of receiver member ia'opposit'e the outlet end of pebble conduit 69 used as receiver member 29. As pebbles are fed from the end of the heater or cooler, the cooling or heating gas fed through conduit 32 may be injected at such a velocity as to carry the pebbles at a rapid rate cut of conduit 59 and against the downstream wall of member 29 so as to provide the desired compression for the pebbles.

The pebble feeder members disclosed above may be conventional star valves or a rotating grooved wheel maintained againstthe surface of the pebbles by a tension member. Pebble receiver member is may be adjustably mounted in the lower end of compression applicator 25 so as to allow the adjustment of compression for the peb bles in the compression applicator. The greater the thermal and mechanical shock which can be applied in one circuit of the test system the more economical the testing becomes. Other and further modifications will be obvious to those skilled in the art upon study of the disclosure and such modifications may be made Without deviating from the spirit and scope of this disclosure.

We claim:

1. A pebble strength testing device which com-'- prises in combination a first heat exchanger; a pebble compression applicator; a first conveyor means communicating between said first heat exchanger and said compression applicator; a second heat exchanger intermediate the ends of said first conveyor means; a second conveyor means, communicating with the upper portion of said first heat exchanger; and pebble sorting means communicating between said compression applicator and said second conveyor means.

The pebble strength testing device of claim 2, wherein said compression applicator comprises a pebble feeder in its upper end, and a hard surfaced receiver member disposed at least three and one half feet vertically below said pebble feeder.

3. The pebble strength testing device of claim 1, wherein said compression applicator comprises a pebble collector having a constricted opening in its lower end", and a hard surfaced member disposed at least six feet Vertically below said opening in saidp'ebbl'e collector.

l; The pebble strength testing device of claim 1, wherein said compression applicator comprises a hard surfaced member, and a compressor operatively connected to said hard surfaced member.

5. A pebble strength testing device which comprises in combination a heater; a pebble com pression applicator; a first conveyor means communicating between said heater and said compression applicator; at least one coolant conduit communicating between a coolant supply source and said first conveyor means; a second conveyor means communicating with the upper portion of said heater; and pebble sorting means communicating between said compression applicator and said second conveyor means.

6. The pebblestrength testing device of claim 1, wherein a pebble feeder is provided intermediate the ends of said first conveyor means.

'7. A pebble strength testing device which comprises in combination an inclined heater; an

elevator; a firstp'ebble conduit communicating between the lower portion of said heater and the lowerv portion of said elevator; a pebble feeder intermediate the endsof said pebble conduit; at least one coolant conduit communicating between a coolant supply source and said pebble conduit; a pebble compression applicator; a second pebble conduit extending between the upper portion of said elevator and the upper portion of said compression applicator; pebble sorting means com municating with the lower portion of said com pression applicator; and a third pebble conduit communicating between said pebble sorting ineansland the upper portion of said heater.

s. The pebble strength testing device of claim 7, wherein said compression applicator comprises a pebble feeder having a constricted opening in its lower end; and a hard surfaced member dis based at least three and one-half feet vertically below said opening in said pebble feeder.

A pebble strength testing device which cemprises in combination a cooling chamber; a pebble compression applicator; a first conveyor means communicating between said cooling chamber said compression applicator; at least one heating fluid conduit communicating between a heating fiuid supply source aid first conveyor means; a second conveyor means coinmunicating with the upper portion or" said cooling chamber; and pebble sorting means communicating between said compression applicator and said second conveyor means.

10. A method of testing the strength of heat transfer pebbles which comprises introducing said pebbles into a first heat exchange zone; raising the temperature of said pebbles to a temperature within the range of between 1600" F. and 3500 F. at'a rate of between 1000 F. and 1800 F. per minute; passing said heated pebbles at their elevated temperature to a second heat exchange zone; cooling said pebbles within said second heat exchange zone at a rate of between 2000 F. and 3500" F. per minute; conveying said cool ed pebbles to a compressor zone; subjecting said cooled pebbles to a sudden predetermined compression within said compressor zone; separating unbroken pebbles from broken pebbles; and recycling said unbroken pebbles to said first heat exchange zone.

11. The method of claim 10, wherein said pebbles are subjected to a predetermined compression by dropping said pebbles onto a hard surface wi hin said compressor zone from a pre determined height.

, s M P. ROBINSON. ROBERT E. GOINS.

References Cited in the file of this patent UNITED s'raras' PATEEN'IQ Number Name Date 970,373 Hemstreet Sept. 1'3, 1910 1,498,659 Jackson June 24, 1924 2,264,412 Shindel' Dec. 2, 1941 FOREIGN PATENTS Number Country Date 227,139 Great Britain Jan. 12, 1925 

